If you haven't noticed Isak Leivsson's handmade downhill bikes out on the World Cup tracks, surely you remember his legendary backflip attempt
in his race run at Snowshoe, right? Now, he's made a bike that will flip and spin a little better than his several homemade downhill race bikes, which have roughly 500mm chainstays (give or take a centimeter, depending on the version).
Isak Leivsson, a former bike tester for Pole Bicycles, has experimented with building his own bikes for nearly two years now. What started as a way to make himself some custom tools has morphed into about 10 complete bike builds and several other bits and pieces.
After building only full suspension bikes that have been focused on racing, Isak decided he wanted to focus a bit more on fun by building something that would work well for tricks and low-speed riding. 130mm of rear travel, he said, felt like the right compromise between capability and fun: it's poppy enough but can handle some "big-ish" hits. He chose 27.5" wheels because smaller-wheeled bikes spin much more easily than 29ers.
Isak designs for function and the form follows.
The most important part of the design process is figuring out what ride characteristics he wants in the bike and translating that into geometry and kinematics, he said. He then uses Linkage x3, a suspension kinematics software tool, to plug in the dimensions of the bike's side profile and suspension points, tweaking the numbers until he has what he wants. To make reading off the numbers easier, he exports the side profile to CAD software before beginning the build. Later, once the main frame parts are built and in-hand, he goes back to the design stage to create the plate cutouts for the brake mount, pivot points, and shock mount pieces, along with the rocker links.
With the frame profile designed, he makes jigs for the front triangle, seat stay, chainstay, and shock mount, then usually machines the pivot points before welding the front triangle together. After that, it's essentially a matter of notching and welding, he said. He mills the pivot and bearing holes for the rocker out of flat plate, cuts the outer design with a band saw, and finishes the cuts with an angle grinder.
With the number of small spacers and other bits and bobs to make before assembling, Isak said, he's usually eager to ride the bike by the time he's done building and finishes it with just a quick coat of spray paint, if anything.
The front triangle of this particular build was intended for a hardtail and hung on Isak's wall for a while before he decided to turn it into this jib bike. He had a few challenges, like problem-solving how to make the rocker pivot point without making new jigs for this one-off, out-of-order project, but he seems to have sorted it out.
The head tube, bottom bracket, seat-tube insert, hose guides, and direct mount brake mount are from Bikefabsupply, and dropouts and hanger are from Paragon Machine. He made all the suspension mount parts and plate cutouts himself.
Isak said the geometry is similar to that of his downhill bikes, but scaled smaller and with slightly steeper angles for maneuverability. Although this bike is much shorter than the race bikes he's built, he kept the same ratio of front center to rear center, as he likes to be in roughly the same position on all his bikes. "My location within the bike is close to the same, as the wheels are relatively speaking at the same place compared to the largest part of my force input to the bike, my feet," he explained. "I am just balanced by a narrower triangle."
Isak designs his bikes for functionality, focusing on geometry, suspension kinematics, strength, stiffness, and simplicity of use and manufacture, he said. His emphasis on building a bike around specifically what he wants shows in the bars he built for this bike: It's nearly impossible to find bars as tall as what he wants, so he built them himself. It's fun, he learns something, and he gets exactly what he wants. He said these current 115mm rise bars are a bit taller than he'd ultimately like, so he plans to swap out to a 90mm set in the future.
While some might say his 455mm chainstays are too long for a bike of this nature, he said, he likes them that way because their length allows him to finesse and control his input for manuals, bunny hops, and jumps much more easily than on a bike a shorter rear end. He wants to stand upright, and the long chainstays and tall bars allow him to do so. "This setup works out great for me, I can ride the bike in the position I like without having to worry about looping out when I pull back," he said."
Isak says he often receives questions about the tubing he uses, so here are a few answers. This bike is made completely of 0.035" wall tube thickness, but of varying outside diameters. The downtube and seat tube are 1 3/8" (35mm), the top tube is 1 1/4" (31.8mm), chainstays are 1", and the seat stays are 3/4".
In the near future, we'll likely see this bike's bigger sibling from Isak. He says he recently finished a downhill bike that's meant for tricks and jumps - essentially a smaller version of his V5 downhill race bike.
To learn more, find Isak's welding and riding on Instagram at @isakleivsson
. If you don't see any updates, it probably means he's out having too much fun on the jib bike.